Congratulations on beating brain cancer! That is tremendous!
I have carpal tunnel syndrome, and I can’t recommend Guardian Druid enough. It’s fairly easy to keep the rotation keybinds and cooldowns in relatively easy reach. Same with BM Hunter, which is also fun and has the added bonus of pet collecting. I am a big fan of both.
If I had a penny everytime I read this on the forums I’d be rich.
Congrats on beating brain cancer. Hopefully with time you’ll overcome the residual issues you’ve been left with. I had a mild stroke in January and am suffering similar issues to you. Memory problems, fine motor skill problems, vision problems, and when overwhelmed by too many things going on at once, I can’t keep track of it all and therefore lose track of what I’m supposed to be doing at the same time. I’ve been having the easiest time leveling Arcane Mage, Brewmaster Monk, Protection Paladin, Blood DK, and Disc Priest. Unfortunately, I’ve resigned myself to soloing pve world content, as I simply can’t keep up in dungeons or raids and very few groups are patient enough to slow down for the sake of one player when the current playstyle seems to be rushing through everything as quickly as possible. Which is fine, it’s much more enjoyable just to plod through things at my own pace solo, rather than feeling guilty over slowing a group down which I feel takes away from the sense of fun.
Druid you don’t need a lot of button pressing to be good and you can play all specs. I had a friend who had blood clots in the brain years ago and they forgot everything in a dungeon. Every dungeon and raid I explained the fight to them and helped them with everything. One of the best tanks I ever played with. He finally got the treatment he needed and no longer needs me but it was great times. Has a few guild members and randoms who was mean but it’s easy to replace DPS 
Just wanted to express massive congratulations on beating cancer that’s truly awesome. I wish you health and happiness.
Unfortunately I don’t have advice on the game specific needs you asked about.
Congratulations on your recovery!
I main healers, and dedicate my fun time to a Fury Warrior (I use the GSE addon to create more robust macros, similar to castsequence macros, but a bit more sophisticated, which makes using all the cool downs easier).
Addons are a lot of help, for a healer I definitely recommend Vuhdo and WeakAuras. Vuhdo allows one to easily click cast every target spell, I use Growl’s Dungeon frames (Yumytv, see https://youtube.com/@yumytv) ( and his UI video: https://youtu.be/_cn344NOZd8).
As for healers, I have played all of the healers in Dragonflight and I would recommend Resto Druid as one of the most forgiving, followed by Holy Priest. Resto Druid is very similar to it’s older play style, where Holy Priest has seen a number of changes over the years, making it the harder of the two if you are familiar with their older play styles.
I do not recommend Holy Paladin, Discipline Priest, Resto Shaman, Preservation Evoker or Mistweaver Monk. All of them have additional expectations that would be placed on them in group play. Holy Paladin and Mistweaver Monk are strongest in melee, increasing the difficulty of their play, because one must learn melee mechanics while building muscle memory for healing. Restoration Shaman (my oldest played healer) has so so much ability bloat, but at their core they are relatively easy and after improving muscle memory can bring a lot to a group. Preservation Evoker is strong, but they are a mid-range healer that is a new play style, with the play style being somewhat similar to the ramping style of Discipline Priest. Both the Evoker and Discipline are strong but are hard to master and easy to make mistakes with.
I also have to second the opinion of Druid is good because of stealth. Always nice to be able to switch to cat and stealth or bear and be a bit more durable.
I struggle with multiple issues with my hands and I actually stopped playing for a long time until I found a website called Wow lazy macros. The creators of this website have made it possible for me to play Wow again and after some initial setup I am able to hold down a single button on my gamepad and use keybinds as a way of running through my rotation without having to constantly spam buttons. This program is NOT I REPEAT NOT against the TOS. No matter what others say or think. This would allow you to actually play whatever class you enjoy rather than have to choose a class with less abilities. I watched YouTube to learn all about it and it has made a world of difference for me.